The invention generally relates to semiconductor packages, and more particularly to optoelectric semiconductor packages with greater mechanical compliance and reduced thermal loss at the ground connections.
Known optoelectric semiconductor packages typically include an optical subassembly which contains a laser chip and a conductive platform. The chip delivers an optical signal to a lens in the optical subassembly, and the signal is then launched from the lens into a high speed connector, such as a metallic wire or pin. The high speed connector leads from the platform to connect the chip with a semiconductor device that utilizes optical signals. Examples of known laser packages may be found in U.S. Pat. Nos. 6,106,161 (Basavanhally et al.) and 5,881,193 (Anigbo et al.). The chip is generally grounded through the platform to the package body. Typically, the ground connection is accomplished through a solder bridge or a conductive epoxy bridge.
The temperature at which the chip operates may be governed by a thermoelectric cooling (TEC) device, which serves to control and/or stabilize the wavelength of the light emitted by the chip. An example of the use of TEC devices in an optoelectric semiconductor package may be found in U.S. Pat. No. 6,055,815 (Peterson). The chip, conductive platform and TEC device may be located within a package. The package provides physical protection to the assembled components as well as attendant connectors.
As the TEC device heats and cools, thermal stresses are created and the ground connection between the conductive platform and the package body flexes due to differing thermal expansions of the relevant materials making up the conductive platform and the package body. Over time, the flexing of the ground connection, i.e., the solder or epoxy bridge, may cause the bridge to break.
The invention provides a semiconductor package which includes a chip, a conductive support structure, a heat transfer device, and a package body having a cavity. The chip, conductive support structure and heat transfer device are positioned within the cavity. An optoelectric connector extends from the cavity out of the package body. At least one ground connector connects the conductive support structure with the package body. The ground connector is adapted to flex with thermal changes.
The invention also provides a method for reducing thermal loss through ground connections in an optoelectric semiconductor package. The method includes providing a chip and a conductive support structure within a cavity of a package body. The cavity may have a wall with a ledge. At least one ground connector may be positioned between the conductive support structure and the ledge. According to one aspect of the invention, the ground connector is formed of stainless steel foil.
According to another aspect of the invention, a semiconductor package having ground connectors is adapted to be compliant or flexible under thermal stress. The method includes providing a cavity including an interior wall spaced apart from a conductive support structure, and attaching at least one ground connector to the conductive support structure and the cavity interior wall. If desired, the ground connector may be formed of a conductive foil which flexes with thermal stress.
These and other advantages and features of the invention will be more readily understood from the following detailed description which is provided in connection with the accompanying drawings.